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[FLINK-38516][Table SQL/Gateway] Add config for read-only sql gateway #27118

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[FLINK-38516][Table SQL/Gateway] Add config for read-only sql gateway #27118

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@rosakng rosakng commented Oct 14, 2025 •
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https://issues.apache.org/jira/browse/FLINK-38516

What is the purpose of the change

The Flink SQL Gateway currently lacks native support for read-only mode to restrict ModifyOperations (e.g., INSERT, DELETE). This feature allows ad-hoc querying on shared session clusters without risk of data modification.

This pull request adds a a configuration parameter sql-gateway.read-only such that if enabled, it rejects SQL statements attempting to modify data or schema.

Brief change log

Creates read-only sql gateway configuration that blocks execution of modification queries if enabled.

Verifying this change

Submit a FlinkSQL modification query to a session cluster and check that executing the query throws an exception i.e.
image

  • Added a unit test for an error returned such that client configuration is set (sql-gateway.read-only: true) and if the query is a modifying operation.

Full stack trace:

Click to expand 
Internal server error.; <Exception on server side:
org.apache.flink.table.gateway.api.utils.SqlGatewayException: org.apache.flink.table.gateway.api.utils.SqlGatewayException: Failed to fetchResults.
	at org.apache.flink.table.gateway.rest.handler.statement.FetchResultsHandler.handleRequest(FetchResultsHandler.java:91)
	at org.apache.flink.table.gateway.rest.handler.AbstractSqlGatewayRestHandler.respondToRequest(AbstractSqlGatewayRestHandler.java:84)
	at org.apache.flink.table.gateway.rest.handler.AbstractSqlGatewayRestHandler.respondToRequest(AbstractSqlGatewayRestHandler.java:52)
	at org.apache.flink.runtime.rest.handler.AbstractHandler.respondAsLeader(AbstractHandler.java:196)
	at org.apache.flink.runtime.rest.handler.LeaderRetrievalHandler.lambda$channelRead0$0(LeaderRetrievalHandler.java:87)
	at java.base/java.util.Optional.ifPresent(Optional.java:178)
	at org.apache.flink.util.OptionalConsumer.ifPresent(OptionalConsumer.java:45)
	at org.apache.flink.runtime.rest.handler.LeaderRetrievalHandler.channelRead0(LeaderRetrievalHandler.java:84)
	at org.apache.flink.runtime.rest.handler.LeaderRetrievalHandler.channelRead0(LeaderRetrievalHandler.java:49)
	at org.apache.flink.shaded.netty4.io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:99)
	at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:444)
	at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
	at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
	at org.apache.flink.runtime.rest.handler.router.RouterHandler.routed(RouterHandler.java:115)
	at org.apache.flink.runtime.rest.handler.router.RouterHandler.channelRead0(RouterHandler.java:94)
	at org.apache.flink.runtime.rest.handler.router.RouterHandler.channelRead0(RouterHandler.java:55)
	at org.apache.flink.shaded.netty4.io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:99)
	at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:444)
	at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
	at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
	at org.apache.flink.runtime.rest.handler.logging.RestLogHandler.channelRead0(RestLogHandler.java:35)
	at org.apache.flink.runtime.rest.handler.logging.RestLogHandler.channelRead0(RestLogHandler.java:12)
	at org.apache.flink.shaded.netty4.io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:99)
	at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:444)
	at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
	at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
	at org.apache.flink.shaded.netty4.io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:103)
	at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:444)
	at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
	at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
	at org.apache.flink.runtime.rest.FileUploadHandler.channelRead0(FileUploadHandler.java:233)
	at org.apache.flink.runtime.rest.FileUploadHandler.channelRead0(FileUploadHandler.java:70)
	at org.apache.flink.shaded.netty4.io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:99)
	at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:444)
	at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
	at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
	at org.apache.flink.shaded.netty4.io.netty.channel.CombinedChannelDuplexHandler$DelegatingChannelHandlerContext.fireChannelRead(CombinedChannelDuplexHandler.java:436)
	at org.apache.flink.shaded.netty4.io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:346)
	at org.apache.flink.shaded.netty4.io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:318)
	at org.apache.flink.shaded.netty4.io.netty.channel.CombinedChannelDuplexHandler.channelRead(CombinedChannelDuplexHandler.java:251)
	at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:442)
	at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
	at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
	at org.apache.flink.shaded.netty4.io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1410)
	at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:440)
	at org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
	at org.apache.flink.shaded.netty4.io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:919)
	at org.apache.flink.shaded.netty4.io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:166)
	at org.apache.flink.shaded.netty4.io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:788)
	at org.apache.flink.shaded.netty4.io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:724)
	at org.apache.flink.shaded.netty4.io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:650)
	at org.apache.flink.shaded.netty4.io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:562)
	at org.apache.flink.shaded.netty4.io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997)
	at org.apache.flink.shaded.netty4.io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
	at java.base/java.lang.Thread.run(Thread.java:840)
Caused by: org.apache.flink.table.gateway.api.utils.SqlGatewayException: Failed to fetchResults.
	at org.apache.flink.table.gateway.service.SqlGatewayServiceImpl.fetchResults(SqlGatewayServiceImpl.java:238)
	at org.apache.flink.table.gateway.rest.handler.statement.FetchResultsHandler.handleRequest(FetchResultsHandler.java:89)
	... 54 more
Caused by: org.apache.flink.table.gateway.service.utils.SqlExecutionException: Failed to execute the operation 58ac14fe-6416-4746-904d-e7b5da0fd355.
	at org.apache.flink.table.gateway.service.operation.OperationManager$Operation.processThrowable(OperationManager.java:415)
	at org.apache.flink.table.gateway.service.operation.OperationManager$Operation.lambda$run$0(OperationManager.java:268)
	at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:539)
	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
	at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:539)
	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
	... 1 more
Caused by: org.apache.flink.table.gateway.service.utils.SqlExecutionException: SQL Gateway is in read-only mode. Modify operations are not allowed.
	at org.apache.flink.table.gateway.service.operation.OperationExecutor.callModifyOperations(OperationExecutor.java:678)
	at org.apache.flink.table.gateway.service.operation.OperationExecutor.executeOperation(OperationExecutor.java:509)
	at org.apache.flink.table.gateway.service.operation.OperationExecutor.executeStatement(OperationExecutor.java:263)
	at org.apache.flink.table.gateway.service.operation.OperationExecutor.executeStatement(OperationExecutor.java:218)
	at org.apache.flink.table.gateway.service.SqlGatewayServiceImpl.lambda$executeStatement$1(SqlGatewayServiceImpl.java:221)
	at org.apache.flink.table.gateway.service.operation.OperationManager.lambda$submitOperation$1(OperationManager.java:120)
	at org.apache.flink.table.gateway.service.operation.OperationManager$Operation.lambda$run$0(OperationManager.java:259)
	... 7 more

End of exception on server side>

Does this pull request potentially affect one of the following parts:

  • Dependencies (does it add or upgrade a dependency): no
  • The public API, i.e., is any changed class annotated with @Public(Evolving): no
  • The serializers: no
  • The runtime per-record code paths (performance sensitive): no
  • Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: no
  • The S3 file system connector: no

Documentation

  • Does this pull request introduce a new feature? yes
  • If yes, how is the feature documented? docs

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flinkbot commented Oct 14, 2025 •
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CI report:

Bot commands The @flinkbot bot supports the following commands:
  • @flinkbot run azure re-run the last Azure build

liuml07
liuml07 reviewed Oct 18, 2025
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Overall looks like a useful feature for some use cases. Left some comment.

...ateway/src/main/java/org/apache/flink/table/gateway/service/operation/OperationExecutor.java

if (isReadOnlyMode) {
throw new SqlExecutionException(
"SQL Gateway is in read-only mode. Modify operations are not allowed.");
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I feel it's useful to show the modifyOperations in the error message in case it's unclear to users which are actually violating the read-only mode.

@github-actions github-actions bot added the community-reviewed PR has been reviewed by the community. label Oct 18, 2025
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@rosakng @flinkbot @liuml07